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Template Metaprogramming with C++

You're reading from   Template Metaprogramming with C++ Learn everything about C++ templates and unlock the power of template metaprogramming

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Product type Paperback
Published in Aug 2022
Publisher Packt
ISBN-13 9781803243450
Length 480 pages
Edition 1st Edition
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Author (1):
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Marius Bancila Marius Bancila
Author Profile Icon Marius Bancila
Marius Bancila
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Table of Contents (16) Chapters Close

Preface 1. Part 1: Core Template Concepts
2. Chapter 1: An Introduction to Templates FREE CHAPTER 3. Chapter 2: Template Fundamentals 4. Chapter 3: Variadic Templates 5. Part 2: Advanced Template Features
6. Chapter 4: Advanced Template Concepts 7. Chapter 5: Type Traits and Conditional Compilation 8. Chapter 6: Concepts and Constraints 9. Part 3: Applied Templates
10. Chapter 7: Patterns and Idioms 11. Chapter 8: Ranges and Algorithms 12. Chapter 9: The Ranges Library 13. Assignment Answers 14. Other Books You May Enjoy Appendix: Closing Notes

Exploring requires expressions

A requires expression may be a complex expression, as seen earlier in the example with the container concept. The actual form of a requires expression is very similar to function syntax and is as follows:

requires (parameter-list) { requirement-seq }

The parameter-list is a comma-separated list of parameters. The only difference from a function declaration is that default values are not allowed. However, the parameters that are specified in this list do not have storage, linkage, or lifetime. The compiler does not allocate any memory for them; they are only used to define requirements. However, they do have a scope, and that is the closing curly brace of the requires expression.

The requirements-seq is a sequence of requirements. Each such requirement must end with a semicolon, like any statement in C++. There are four types of requirements:

  • Simple requirements
  • Type requirements
  • Compound requirements
  • Nested requirements
  • ...
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